Description:
A vulnerability has been discovered in Firefox, which can be exploited by malicious people to compromise a user's system.

The problem is that Firefox registers the "firefoxurl://" URI handler and allows invoking firefox with arbitrary command line arguments. Using e.g. the "-chrome" parameter it is possible to execute arbitrary Javascript in chrome context. This can be exploited to execute arbitrary commands e.g. when a user visits a malicious web site using Microsoft Internet Explorer.

The vulnerability is confirmed in Firefox version 2.0.0.4 on a fully patched Windows XP SP2. Other versions may also be affected.

EDIT: Forgot to refresh, and missed your answer. Listing on that site doesn't necessarily mean it's been used in the wild. A lot of their info comes from security research groups, which try to find vulnerabilities before they're exploited.